Add export job status API endpoint

Implements GET /api/exports/[jobId] to retrieve export job status and download URL. Includes authentication and ownership checks, returning job details or appropriate error responses.

Author: rafiqul4

src/app/api/exports/[jobId]/route.ts

@@ -0,0 +1,45 @@
+/**
+ * GET /api/exports/[jobId]
+ * 
+ * Get export job status and download URL
+ * 
+ * Implements job status polling for async exports (T029)
+ * 
+ * @requires Authentication
+ * @returns Export job details with status and file URL (if completed)
+ */
+
+import { NextRequest } from 'next/server';
+export const dynamic = 'force-dynamic';
+
+import { createApiHandler, middlewareStacks } from '@/lib/api-middleware';
+import { 
+  successResponse,
+  notFoundResponse,
+  forbiddenResponse,
+} from '@/lib/api-response';
+import { getExportJobStatus } from '@/services/export-service';
+
+export const GET = createApiHandler(
+  middlewareStacks.authenticated,
+  async (request: NextRequest, context) => {
+    const jobId = context.params?.jobId;
+
+    if (!jobId) {
+      return notFoundResponse('Job ID is required');
+    }
+
+    const userId = context.session!.user.id;
+
+    // Fetch job status (enforces ownership)
+    const job = await getExportJobStatus(jobId, userId);
+
+    if (!job) {
+      return notFoundResponse('Export job not found');
+    }
+
+    return successResponse(job, {
+      message: 'Export job retrieved successfully',
+    });
+  }
+);